Fred enjoyed a fruitful spell at Shakhtar, winning six trophies during a five-year stint in Ukraine.

United, meanwhile. failed to claim a trophy last term following their League Cup and Europa League triumphs in Mourinho's first season at the club.

"It's going to be a big challenge, that's for sure," Fred said of joining United. "But I am someone who is always looking to improve.

"I'm looking to show the best of my abilities every day and to work to improve, and that means working to play well and put in good performances in the Premier League and to achieve great things and win titles.

"At United, I’m looking to win titles, alongside my new team-mates and my new manager, win matches with the club and make history by achieving great things together."